There is scientific evidence that a calorically restricted diet can increase longevity in the species in which it has been investigated (humans, rodents, and probably other species of domestic animals).
Does that mean it applies to snakes? No, of course not.
But it doesn't make it untrue in snakes. I don't know of any specific data for snakes, but I tend to err on the side of caution. If it is true for some vertebrates, it may be true in others.